1. Field of the Invention
The present invention relates to a guide actuator, and more particularly to a measurable guide actuator suitable for an electronic equipment, robot, automatic machine or the like.
2. Description of the Related Prior Art
A guide actuator consists of a base, a sliding table, a driving mechanism, guide mechanism, and a motor. The conventional design used the linear guide way as guide mechanism. A pair of parallel rails of the linear guide ways is mounted on the base, then the sliding table mount on the sliders of the linear guide ways, and the driving mechanism transfers the rotational movement provided by the motor into a linear movement for driving the sliding table to move. The mechanism is complicated, and made more cost. For reducing the cost of machining, the materials of the base and guide mechanism can used by the aluminum extrusion for the mass production, but the rigidity of aluminum is smaller, thus causing the linear and parallel accuracy being worse under the condition of heavy load, so that the positioning precision of the guide actuator is not good.
The driving of the guide actuator may use a screw or a belt. The screw usually uses a ball screw or ACME screw, and the belt usually uses a timing belt for obtaining a better driving motion. The different driving methods result in the different accuracy and velocity of the guiding table. The use of ball screw has the best precision due to the feature of low backlash, and the timing belt due to a worse accuracy because the rubber has flexibility. Under the consideration of velocity, the timing belt has the maximum driving velocity. Under the consideration of cost, the ACME screw has the lowest cost, but the precision and velocity thereof are much worse than that of the ball screw. The guide mechanism of the guide actuator is mainly constituted by a pair of linear guide way. The motor includes a step motor or a servo motor. When the guide actuator is mounted on the machine table equipment, the position of the sliding table is indirectly calculated by the angle of rotation of the motor, which easily causes errors.
In general, the guide actuator does not include directly a position detecting function. Some mechanism mounts an encoder on the motor or the screw shaft, but when the motor drives the screw or the belt wheel to rotate, the control system can only detect the angle of rotation of the motor or the screw shaft, and cannot detect the exact position of the sliding table. If it is needed to detect the exact position of the sliding table, the only conventional method is to additionally install a position scale on the outside of the mechanism after the guide actuator is installed on the equipment. Thus, this method needs to additionally increase the space and time of installation, thereby increasing the consumption of material and the requirements of technology of installation, while the space of the mechanism and the cost of fabrication are also increased.
The primary objective of the present invention is to provide a measurable guide actuator containing a position sensing function therein and having an excellent structural strength without increasing the existing space of construction so as to solve the problems encountered by the conventional guide actuator in which the position of the sliding table of the conventional guide actuator cannot be feedback or the feedback values are incorrect, and to solve the drawbacks in which the conventional guide actuator has a complicated construction and has a high cost of fabrication.
The guide mechanism of the present invention is constructed to have a U-shaped structure which has a great structural inertia moment for providing the measurable guide actuator with an excellent structural rigidity. The U-shaped guide mechanism defines a first groove, and the sliding table defines a second groove mating with the first groove of the U-shaped guide mechanism. A plurality of balls are inserted between the first groove of the U-shaped guide mechanism and the second groove of the sliding table so that the sliding table can be moved relative to the U-shaped guide mechanism by rolling of the balls.
The ruler body of the position measuring member is bonded on the bottom face of the U-shaped guide mechanism, and the sensor of the position measuring member is attached on the sliding table so that the sliding table is integral with the magnetic sensor, thereby saving the space.
In driving, the driving mechanism includes a ball screw or ACME screw extending through the sliding table, and the thread is directly provided on the sliding table to mate with that of the screw. The ball screw needs a circulation channel for the balls, and the ball circulation channel is also provided on the sliding table, thereby saving the space. When the screw is rotated, the thread of the screw will drive the sliding table to move.
When the system is driven by a belt, a timing belt is reeved around the top and bottom faces of the sliding table and is stretched and supported by two belt wheels. When a motor is rotated, the timing belt is driven by the belt wheels to move the sliding table.
The magnetic scale can be used to directly measure the displacement position so as to compensate the precision of the ball screw, the ACME screw or the timing belt. In addition, the driving, guidance and measurement are integrally designed, thereby simplifying the construction and saving cost of fabrication.
In addition, the magnetic scale may also be replaced by a optical scale. A steel strap type optical ruler body is integrally bonded in the inner side of the middle of the U-shaped guide mechanism while the reading sensor is sealed in the sliding table, thereby obtaining more precise signal.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.